Preheat oven to 350F (180C).,Lightly grease or spray 13 x 9 inch (3.5 L) metal baking pan.,Topping: In small bowl, combine walnuts, rolled oats, brown sugar, melted butter and cinnamon until crumbly; set aside.,Bars: In large bowl, whisk together brown sugar, eggs, milk, melted butter, orange rind and vanilla.,Without stirring, add flour, raisins and oats.,Sprinkle with baking poweder, cinnamon and salt.,______,Pour into prepared pan; smoothing top.,Sprinkle with topping.,Bake for 30 min or until tester comes out clean.,Let cool in pan.,Cut into bars.